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Poster: Moongleam Date: May 31, 2010 12:34pm
Forum: feature_films Subject: A note on telecining

As you may have noticed, billbarstad and I are now trying to improve the quality of our uploaded films by using telecine reversal on NTSC 30 fps films (actually 30000/1001 fps).

Telecining converts 24 fps video to NTSC 30 fps video.
To illustrate, let's use four progressive frames that are 12 pixels wide and 8 pixels in height:

AAAAAAAAAAAA
AAAAAAAAAAAA
AAAAAAAAAAAA
AAAAAAAAAAAA
AAAAAAAAAAAA
AAAAAAAAAAAA
AAAAAAAAAAAA
AAAAAAAAAAAA

BBBBBBBBBBBB
BBBBBBBBBBBB
BBBBBBBBBBBB
BBBBBBBBBBBB
BBBBBBBBBBBB
BBBBBBBBBBBB
BBBBBBBBBBBB
BBBBBBBBBBBB

CCCCCCCCCCCC
CCCCCCCCCCCC
CCCCCCCCCCCC
CCCCCCCCCCCC
CCCCCCCCCCCC
CCCCCCCCCCCC
CCCCCCCCCCCC
CCCCCCCCCCCC

DDDDDDDDDDDD
DDDDDDDDDDDD
DDDDDDDDDDDD
DDDDDDDDDDDD
DDDDDDDDDDDD
DDDDDDDDDDDD
DDDDDDDDDDDD
DDDDDDDDDDDD

Telecining converts these to 5 frames:

AAAAAAAAAAAA
AAAAAAAAAAAA
AAAAAAAAAAAA
AAAAAAAAAAAA
AAAAAAAAAAAA
AAAAAAAAAAAA
AAAAAAAAAAAA
AAAAAAAAAAAA

BBBBBBBBBBBB
BBBBBBBBBBBB
BBBBBBBBBBBB
BBBBBBBBBBBB
BBBBBBBBBBBB
BBBBBBBBBBBB
BBBBBBBBBBBB
BBBBBBBBBBBB

BBBBBBBBBBBB
CCCCCCCCCCCC
BBBBBBBBBBBB
CCCCCCCCCCCC
BBBBBBBBBBBB
CCCCCCCCCCCC
BBBBBBBBBBBB
CCCCCCCCCCCC

CCCCCCCCCCCC
DDDDDDDDDDDD
CCCCCCCCCCCC
DDDDDDDDDDDD
CCCCCCCCCCCC
DDDDDDDDDDDD
CCCCCCCCCCCC
DDDDDDDDDDDD

DDDDDDDDDDDD
DDDDDDDDDDDD
DDDDDDDDDDDD
DDDDDDDDDDDD
DDDDDDDDDDDD
DDDDDDDDDDDD
DDDDDDDDDDDD
DDDDDDDDDDDD

Frames 1, 2, and 5 are progressive, while frames 3 and 4 are interlaced. A reverse-telecine filter is able to recreate the original C-frame by extracting its lines from the two interlaced frames; it replaces the two "dirty" frames, and the original 24 fps progressive video is restored. This is better than using a de-interlacing filter, which uses blending to eliminate the comb effect.

The task is made difficult by the fact that the pattern of progressive and interlaced frames is often inconsistent because of edits. So the filter has to be able to distinguish between progressive and interlaced frames by using image analysis.

Most movies that you buy on DVDs today are 24 fps progressive. Your NTSC DVD-player performs telecining before it sends the signal to your television. Some films are mostly progressive with brief bits of 30 fps content.

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Poster: billbarstad Date: May 31, 2010 9:49pm
Forum: feature_films Subject: Re: A note on telecining

There are two things to look for in determining if a movie file or DVD has telecined content: a frame rate of 29.970fps and interlacing. If both are present, the movie is telecined. I use a video analysis program, MediaInfo Mac, for this. MediaInfo is available for Windows and Linux, too.

This post was modified by billbarstad on 2010-06-01 04:49:30